Anyone care to explain the apparent contradiction between these two statements in the Origins section

"The current asteroid belt is believed to contain only a small fraction (by mass) of the primordial asteroid belt. Based on computer simulations, the original asteroid belt may have contained mass equivalent to the Earth. Primarily because of gravitational perturbations, most of this material was ejected from the belt within a period of about a million years of formation, leaving behind less than 0.1% of the original mass... Also, most bodies formed inside the radius of this gap were swept up by Mars (which has an aphelion out at 1.67 A.U.) or ejected by its gravitational perturbations in the early history of the Solar System."

and this statement in the Early Fifth Terrestrial Planet Theory

"There are some key problems with this hypothesis... Another [problem] is the low combined mass of the current asteroid belt, which has only a small fraction of the mass of the Earth's moon."

I don't see a contradiction. One refers to the original mass (about that of the Earth) and the other to the current mass (about 4 percent that of the Moon). Serendipodous 16:56, 1 October 2007 (UTC)

The contradiction that I'm referring to is that the "standard" theory states that the original asteroid belt had an earth-like mass but because of orbital perturbations caused by Jupiter, Mars sweeping up a portion of the belt, etc the mass is now much much smaller. In the next section however, the argument used to discredit the Fifth Planet Theory is that the belt has insufficient mass. If the lost mass is not an issue for the "standard" theory, why is it an issue for the Fifth Planet theory? FusionKnight 17:41, 1 October 2007 (UTC)

In the second instance, I think the concern is that the destruction of the conjectured fifth planet (long after the formation of the solar system) should have left more mass in orbit. The standard(?) model says that most of the mass that could potentially have formed a planet was tossed out during the very early history of the system, because of Jupiter's inward migration and the sweeping orbital resonances, &c. After Jupiter stopped migrating, so too would the resonances. Thus the resonances wouldn't have intersected as much of a destroyed planet's debris and more mass would be left behind. — RJH (talk) 21:16, 1 October 2007 (UTC)

The way I'm reading the article (and I could be misreading) is that the orbital resonance of Jupiter in its current position and the sweeping effect of Mars are what supposedly caused the asteroid belt to lose mass in the "standard" theory. I don't see anything in this article (I'm not saying it doesn't exist elsewhere) which refers to the migration of Jupiter being posited as the main cause of mass-loss.My bad. My eye must have skipped over that sentence in the second paragraph of the Formation section. Regardless, the area between Mars and Jupiter currently contains many areas of orbital resonance with Jupiter. Any bodies entering these areas are ejected from the belt. Orbital resonances exist anywhere two bodies have an orbital period related by a ratio of two integers. (See Orbital Resonance) This article also explicitly states that "the 4:1 orbital resonance with Jupiter, at a radius 2.06 AU, can be considered the inner boundary of the main belt... Perturbations by Jupiter send bodies straying there onto unstable orbits", so we know that orbital resonances with Jupiter have not disappeared.

As it reads now, this article is self-contradictory since it says Jupiter and Mars' influence explain missing mass in the standard theory but not in the fifth planet theory.FusionKnight 21:32, 2 October 2007 (UTC)

Why a belt?

I've wondered: why exactly are so many of the asteroids arranged in this belt? What was the origin, and why would it tend to form in its present location? Meelar(talk) 18:04, May 1, 2005 (UTC)

It would be pretty heavy there for a planet-sized object, one needs really solid(strong?) body to sustain Venu,s x Jupiter..Neptune weight when occasionally combined...

Until this gap is filled, Venu,s should be kept as it is doing now...

Are you sci-fi inclined? It could be a parking orbit for a really large space-ship also...

(well, one must clean it up first from rocks and gravel, unless the space-ship is small enough to fit into Kirkwood gaps...)

S.

Belts around other stars

Wouldn't the observed extrasolar belts be more akin to the Kuiper belt than the asteroid belt? Serendipodous 12:32, 5 September 2006 (UTC)

List of largest asteroids

Shouldn't this article have a list of the largest asteroids within the main belt, sorted by size? I am happy with the new "dwarf planet" status for Ceres, but that doesn't mean that it can't still be categorized with the others. - Lawrence King 07:53, 11 September 2006 (UTC)

Such a list is over at List of noteworthy asteroids. Perhaps a case could be made to include the leading bodies from that list. A possible natural cut-off of sorts occurs after 10 Hygiea, the last of the "big four" most massive asteroids. Deuar 15:13, 11 September 2006 (UTC)

Informative

Not trying to be rude, but shouldnt you article be more informative about asteroids instead of just the asteroid belt? Just so we know at least a little about what is in the asteroid belt?

Yes, in fact Asteroid belt should be merge to Asteroid, they talk almost about the same thing ("minor planet" inside Jupiter). Tttrung 08:41, 27 October 2006 (UTC)

The article here is concerned only with the main orbital grouping of asteroids (red but not blue in the second diagram in the article), which is the "main belt", while Asteroid discusses all the minor bodies inwards of Jupiter. If you're in doubt whether this distinction is useful, have a look at the what links here page for Asteroid belt. Notice how many articles point here via the Main belt redirect. Nevertheless, you have a good point that it was not very informative about the asteroids themselves, so I've added a fairly prominent disambiguation notice in the introduction to try to remedy this. Deuar 14:24, 8 November 2006 (UTC)

Thank you for the information added. Could you give the source for all the numbers (inclination range, semi-major axis range, ...) Are these number "universally agreed", or officially defined by authoritive organisation (like IAU)? 58.187.19.142 02:59, 30 November 2006 (UTC)

I've been planning to partly amend the terminology in this article regarding the use of "main belt" − because this is actually not well defined (as you might have guessed by comments such as "below about 0.33", etc.) Hold on.... ;Regarding the proportion of asteroids in the region mentioned, that comes from a straightforward count of asteroids in an orbit database. I'll track down which one it was... Deuar 17:23, 30 November 2006 (UTC)

asteroid belt or Asteroid Belt

Someone just modified the first sentence to use "Asteroid Belt" instead of "asteriod belt." I think "asteriod belt" should not be capitalized, so I changed the first sentence back . Am I wrong? Most of the article uses the lower case, which seems to agree with the capitalization used in some reference works (i.e. M-W, OED, etc.) —RP88 02:33, 27 February 2007 (UTC) --Arctic Gnome(talk • contribs) 23:45, 11 March 2007 (UTC)

Since there are asteroid belts around multiple stars, I'm guessing it should be lower case in the general sense. If it is specifically about the Asteroid Belt around the Sun, capitalization may be grammatically correct. (Similar to the use of moon or Moon.) — RJH (talk) 17:44, 11 April 2007 (UTC)

GA Review

Good work so far - I would like to see a few fairly minor changes before the article will be ready for Good Article status.

The lead section at present doesn't summarise the article, and instead goes into too much detail about the 'main belt'. The lead should summarise the highlights of the origin and environment sections, and the material about exactly what the 'main belt' is needs to go elsewhere - probably the 'environment' section.

Last section of the first sentence of 'Environment': "new particles must be steadily produced". If what is meant that new particles are in fact being produced, please say so - also any mechanisms suggested by which this dust is being produced. (The current text doesn't really help the reader tell whether you are talking about a corollary of a hypothesis, or a agreed and verified fact).

The collisions section has a discussion of dust generation. So I think this is addressed. — RJH (talk) 19:04, 23 April 2007 (UTC)

The phrase 'asteroid family' might suggest to a reader that asteroids within a family share common composition. Can this be clarified?

References: The article relies heavily on primary sources. I would prefer to see secondary sources: summary papers from journals, books, or reliable newspaper, magazine or website articles. This might not bar being a GA but almost certainly would an FA.

I've never seen the use of primary sources bar an FA, at least on an astronomical topic. But I'll try to find some good-quality external links for further reading. — RJH (talk) 22:53, 19 April 2007 (UTC)

Hope these comments are useful - if there is anything you would like me to clarify, just ask and I'll get back to you right away. The Land 18:53, 4 April 2007 (UTC)

No movement on these points after one week, so I've removed the article from the candidates page and marked it as a 'fail'. However if you can address these points it will easily pass a renomination. The Land 20:15, 10 April 2007 (UTC)

It's unfortunate that the original nominator did nothing to address these concerns. But I think it's ready now. — RJH (talk) 19:09, 23 April 2007 (UTC)

GA on hold

I have reviewed this article according to the GA criteria. I felt kind of guilty for reviewing this article eight days after it was nominated, especially with the large backlog with older articles, but I'm currently covering this in my astronomy class so this was of some interest to me. Besides, it appears that this article just recently had another GA review so it doesn't deserve to wait several more weeks or a month to be reviewed again. Anyway, there are a few things that should be fixed before I pass it.

In third paragraph of the intro, the serial comma is used in "carbonaceous, silicate, and metallic." To maintain uniformity, add a comma after 3 Juno in "2 Pallas, 3 Juno and 4 Vesta". Same goes for "Some of the most prominent families in the main belt (in order of increasing semi-major axis) consist of the Flora, Eunoma, Koronis, Eos and Themis families." and "Eos, Koronis and Themis asteroid families" in the Families and groups section.

I satisfied this by removing the serial comma in the first instance.

Add wikilinks for Sun in the intro and the History of observation sections at their first occurrence. Do the same for perturbations in the same section (it has a wikilink in the intro, but some people bypass the intro when reading the article).

Seems like overkill, but okay.

"It was suggested that comets such as these may have provided a source of water for the formation of the Earth's oceans." Elaborate on this further, by detailing the fact that the comets actually impacted Earth itself to possibly bring the water. Otherwise people unaware of the process may think that oceans formed just because comets existed in this asteroid belt. This also goes for the "Main-belt comets formed within the belt outside the snow line, and these are a leading candidate for the formation of the Earth's oceans." statement in the Origins section.

I expanded this slightly, but I didn't want the article to get too side-tracked on this topic.

"The currently accepted theory of planetary formation is the nebular hypothesis." Is this common knowledge, or do you think that there should be an inline citation for this? It's your choice, I won't limit the article based on this, but you can add one if you like.

I expanded the description a little and added a citation. The link is the better choice though for people who want more details.

In the origin section, there is a lot of astronomical terms that could be considered confusing/jargon to unaware readers. Consider adding more wikilinks or further clarifying some terms. Don't dumb it down too much, so that it maintains its current quality, but just make a few changes you see fit.

I attempted to clarify the terminology. Let me know if there are still issues.

In the rest of the article Solar System is capitalized, but in the intro it is not. Change to whatever is correct.

Done.

"Finally the significant chemical differences between the asteroids is difficult to explain if they come from the same planet." I think there should be a comma after "Finally".

Done.

Add a wikilink for the full date July 16, 1972 in the Exploration section.

Done.

I think if you can, later on, try and expand the exploration section. This isn't necessary now, of course, but it would be interesting to have more information on this. For now, I think you should be able to add an image for one of the spacecraft from the missions listed in the section.

The problem here is that there really hasn't been a lot of exploration of the asteroid belt by spacecraft; just some near-Earth asteroids. Most of the spacecraft were just passing through. The Dawn Mission appears to be the first true mission of exploration to the main belt, and that hasn't launched yet. I was hoping to add more later, but I'm a little reluctant to pad it right now.

Altogether, this is a well-written article with excellent sources and great images. Most of the above suggestions should be very easy to fix. I'll leave this article on hold for seven days and pass it if they are fixed. When you are done or if you have any questions, please let me know on my talk page and I'll get back to you as soon as I can. --Nehrams2020 23:38, 1 May 2007 (UTC)

Thank you. There's no problem with the delay—my experience has been that articles tagged as LONG can sometimes take up to a month. I've attempted to address your issues. — RJH (talk) 14:58, 2 May 2007 (UTC)

GA passed

I have passed this article according to the GA criteria. Excellent work on fixing all of the above suggestions, even though some of my suggestions were nitpicky they were all for improving the article. Keep adding new information with proper sources, and I hope the peer review will help to improve the article further before taking it to FAC eventually. If you have the time, please consider reviewing an article or two at GAC to help with the current backlog. --Nehrams2020 19:39, 3 May 2007 (UTC)

Unclear: 4 Vesta?

While reading this intro, I noted a list of "4 Vesta" while describing the makeup of the asteroid belt. Later on, Vesta is treated as a singular noun. Is Vesta a plural word in the intro but singular in the body of the article? Shoud it be? Or is "4 Vesta" the name of a piece of the Asteroid Belt? This is unclear and confusing to those hoping for an introduction to the Asteroid Belt.—The preceding unsigned comment was added by 66.188.125.248 (talk • contribs).

That's a good point. Unfortunately that is the standard naming convention for asteroids. I tried to add clarification to the list. — RJH (talk) 16:20, 17 June 2007 (UTC)

Unsourced addition

The following paragraph was included in the text:

As it is visible to the naked eye in pollution-free skies, Vesta, like Uranus, had most probably been seen before telescopes were invented but was too faint to be recognised as orbiting the Sun. Johannes Kepler apparently[1] said in 1956 that he believed that there must be a planet between Mars and Jupiter. However, asteroids' (relatively) fast motion (Vesta orbits the Sun 23.16 times for every Uranus orbit) meant seventeenth and eighteenth century astronomers whose telescopes could resolve objects much fainter than 10 Hygiea's maximum brightness of +9.1 never located any asteroid for long enough to recognise it either as orbiting the Sun or as a star. By contrast, Uranus was originally identified as "34 Tauri" in 1692 and only ninety years later found to be a planet.

Unfortunately it is mostly unsourced and in many respects appears to be unconfirmed speculation (or possibly OR). The year given for Kepler's remark is clearly erroneous. So, in order for this article to retain it's GA status, I'd like to leave this here until suitable references can be found that confirm these remarks. Sorry. — RJH (talk) 17:01, 17 June 2007 (UTC)

So the six largest asteroids don't add up to half the mean mass of the belt. At best the four largest are at half the low end of the estimated mass range (1.52). For future reference I changed the wording to "almost half the total mass within the main belt" rather than "about half the total mass". (Yes it's a nit. :-) — RJH (talk) 19:38, 10 July 2007 (UTC)

Meteorites

Some mention of the asteroids' connection to meteorites needs to be made. Serendipodous 20:12, 2 October 2007 (UTC)

'Collisions' section: "...and some of the debris from collisions can form meteoroids that enter the Earth's atmosphere." Meteorites are a subset of the meteoroids. — RJH (talk) 15:55, 3 October 2007 (UTC)

Direction of Orbit

Does anybody have any sources/data on what direction asteroids orbit the sun? I've seen it mentioned in passing that they orbit in either direction, but it would be nice to have some numbers showing how many orbit which direction. I'll do some searching, but if anybody else knows... FusionKnight 02:39, 6 October 2007 (UTC)

Almost all orbit in the prograde direction like all the major and dwarf planets. For a list of the retrograde ones see here (I'm not sure if it's complete, but it certainly shows that the number of retrograde asteroids is tiny in comparison with the several hundred thousand known in total). Deuar 11:10, 6 October 2007 (UTC)

Pictures

Why are there only a few pictures in the article, and only one of an asteroid? There need to be more for this to be a nice article (in my opinion, which is often wrong). I have a collection of rather interesting pictures from Galaxy zoo. However, they do not really show the asteroids themselves, so I did not upload any, and I will wait till someone says something to do so. (Here is a forum topic from GZ that has lots of asteroid pics. http://www.galaxyzooforum.org/index.php?topic=3393.0 ) I started that topic. Megalodon99Talk 19:08, 7 October 2007 (UTC)

Perhaps because the asteroid belt as a whole isn't very photogenic? We could include an image of the zodiacal light, since that is discussed in the article. Also it might be interesting if there were good images in the Commons of S-type and M-type meteorites for comparison. It's too bad we don't have a useable image of (25143) Itokawa; that would be an ideal illustration of a rubble-pile asteroid for the collisions section. — RJH (talk) 01:51, 15 October 2007 (UTC)

Zodiacal light would be a good idea for Collisions. There should be a picture of at least one asteroid, maybe Gaspra. Serendipodous 20:14, 17 October 2007 (UTC)

^George, Demetra and Bloch, Douglas; Asteroid Goddesses: The Mythology, Psychology and Astrology of the Re-Emerging Feminine; New Edition, published 2003 by Ibis Press; p. 203